Electrical outlet box

ABSTRACT

A molded plastic electrical outlet box has upper and lower mounting bosses which engage front and rear faces of the wall panel opening in which the box is installed, thereby temporarily but securely retaining the box in the wall opening. The same pair of screws which subsequently fix an electrical unit within the box also permanently and securely clamp the mounting bosses to the wall panel. Transverse nail guiding passages provide a means for additionally nailing the box to a stud if required by local building codes.

United States Patent MacDonald [54] ELECTRICAL OUTLET BOX [72] inventor:Robert D. MacDonald, Metamora, Mich.

[73] Assignee: Cardinal of Adrian, Inc., Adrian, Mich.

[22] Filed: Apr. 30, 1971 21 Appl. No.: 139,058

[52] U.S. Cl. ..174/58, 220/36, 248/D1G. 6, 248/27 [51] Int. Cl. ..H02g3/12 [58] FleldofSearch ..174/58,53, 153 G; 220/32, 220/33, 3.4, 3.5,3.6, 3.9, 18; 248/27, DIG. 6

[56] References Cited UNITED STATES PATENTS 982,193 1/1911 Thayer..220/3.4 1,519,927 12/1924 Polhemus... 220/36 X 2,044,650 6/1936Thompson ..220/3.6 3,097,259 7/1963 McMillen et al... 174/153 G3,176,869 4/1965 Kinney ..l74/58 X [451 Apr. 25, 1972 3,193,226 7/1965Showalter ..248/27 3,268,189 8/1966 Ducharme ..220/3.3

FOREIGN PATENTS OR APPLICATIONS 730,452 5/1955 Great Britain ..220/3.3

Primary Examiner-E. A. Goldberg Assistant ExaminerD. A. ToneAttorney-Cullen, Settle, Sloman & Cantor [57] ABSTRACT A molded plasticelectrical outlet box has upper and lower mounting bosses which engagefront and rear faces of the wall panel opening in which the box isinstalled, thereby temporarily but securely retaining the box in thewall opening. The same pair of screws which subsequently fix anelectrical unit within the box also permanently and securely clamp themounting bosses to the wall panel. Transverse nail guiding passagesprovide a means for additionally nailing the box to a stud if requiredby local building codes.

8 Claims, 8 Drawing Figures P'A'TENTEDAPR 25 I972 SHEET 10F 2 INVENTOR.

ROBERT 0. MAC LXJNALD.

m N m a M m i mm m ATT' Y3.

PATENTEDAPR 2 5 I972 SHEET 2 BF 2 MQ L INVENTOR.

ROBERT D. MAC DGVALD CULLEMSETTLE, SLOMAN 8 CANT 0?.

ATT'YS.

ELECTRICAL OUTLET BOX BACKGROUND OF INVENTION Electrical outlet boxesare flush mounted in walls for receiving conventional electrical unitssuch as switches or plug receptacles. Such boxes are typically nailed orscrewed into the wall so that their open front face is approximatelyflush with the face of the wall. Pre-weakened knock-out or punchoutholes are formed in the side walls of the box, to permit entry ofelectrical wiring.

Once the outlet box is secured in the wall, the electrical unit is thenscrewed into the box. For this purpose, the front face of the electricalunit has projecting metal mounting straps with clearance holes for thescrews, which pass through the straps into threaded receiving holes inthe box. Thereafter, the entire assembly is covered over with a faceplate usually screwed to the electrical unit.

In high production operations, particularly in the case of mobile homeswhich travel down an assembly line during construction, the aboveconventional practice has several disadvantages. First, a screw typeinstallation operation is required at three separate stages: theinstallation of the outlet box to the wall, the mounting of theelectrical unit within the box and the securing of the cover plate tothe finished installation. Furthermore, in mobile home constructionwherein building codes do not generally require that outlet boxes besecured to a stud, it is permissable to secure the outlet box to thewall facing surrounding it. On the moving assembly line, however, thepreliminarily inserted outlet boxes tend to jiggle out of the wall panelopening unless they are promptly and firmly screwed into place. This isnot always convenient in a high production assembly line type ofoperation.

Hence, it is a principal object of this invention to provide aninexpensive one-piece molded plastic electrical outlet box especiallyadapted for use in mobile home construction, and which has means toassure that it will remain in the wall panel opening prior to finalcompletion of the installation. An additional object of this inventionis to reduce the number of assembly operations required in theinstallation of the box in the wall and the subsequent securing of theelectrical unit within the box.

These and other objects of the present invention will become apparentfrom the following specification and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of theimproved electrical outlet box of this invention. v

FIG. 2 is a front view into the open front end of the box of FIG. 1.

FIG. 3 is a side view of the box.

FIG. 4 is a side cross-sectional view in the direction of arrows 4-4 ofFIG. 2.

FIGS. 5 through 8 are fragmentary side cross-sectional views similar toFIG. 4, but showing the sequence of steps involved in installing theoutlet box into a wall opening and subsequently securing the electricalunit within the outlet box.

DETAILED DESCRIPTION OF THE INVENTION Referring in particular to FIGS.1-4 of the drawings, there is shown a one-piece molded plasticelectrical outlet box 10, generally comprising top wall 12, bottom wall14, rear wall 16, and side walls 18 and 20. As is conventional, :suchwalls of the box would be provided with knock-outs to provide accessholes for electrical wiring at whatever point is required. Since suchknock-outs are conventional and do not form a portion of this invention,they have not been illustrated.

Top wall 12 has a pair of integrally molded laterally spaced frontbosses or tabs 22 and a rearward boss 24 positioned between but behindfront bosses 22. A substantially symmetrical arrangement is similarlyprovided on bottom wall 14 of box 10, comprising a pair of front bosses26 and a rearward bottom boss 28.

Top wall 12 is further provided with a pair of side nail guiding bosses30, from which extend forwardly resilient spring arms 32. Bottom wall 14is similarly provided with a pair of side nail guiding bosses 34, but nocorresponding spring arms are required.

As best seen in FIG. 5, electrical outlet box 10 is adapted to beinserted in wall panel 36, having a front face 38, an upper opening edge40 and a lower opening edge 42. A small scallop or groove 44 is providedin lower edge 42 of the opening, for a purpose which will be describedbelow.

Wall panel 36 represents one face of a double faced wall, which wouldtypically comprise a series of framing members such as two-by-fours,both faces of which would be coyered with a facing such as wall panel36. In the case of mobile homes, wall panel 36 may comprise inch or 3/l6 inch plywood. The open front face of outlet box 10 is intended to lieapproximately flush with front face 38 of wall panel 36, with the bodyof the box lying in the space between the opposed wall panels of thedouble faced wall, as is conventional. 6

The technique of preliminarily installing outlet box 10 in the openingin wall panel 36 is shown in a series of sequential steps illustrated inFIGS. 5-8.

By way of example only, it is useful to indicate the approximatedimensions of a typical installation, since certain of these dimensionsare significant in achieving the objectives of this invention. For awall opening having a width of 2 and 7/16 inches and a height of 3 and5/16 inches, the width of box 10 may be 2 and inches; the height fromthe upper face of top wall 12 to the lower face of bottom wall 14 may be3 inches; the height of upper bosses 22 and 24 may be one-half an inch;and the height of lower bosses 26 and 28 may be one-quarter inch; andthe overall depth of the box may be 2 V4 inch.

The installation of the box requires that it be inserted from the rearof the opening. If the wall has not been completely assembled, this canbe readily accomplished. Otherwise, the box can be passed through thewall opening with its open front face either downward or upward.

Comparing FIGS. 5 and 6, it will be seen that the box is initiallytilted forwardly at the top and lifted until the upper surface of topwall 12 abuts the upper edge 40 of the wall opening. In so doing,resilient spring arms 32 are depressed by the edge 40 of the wallopening.

Once the box has been placed in the position shown in FIG. 6, the lowerportion of the box can be rocked forwardly, since lower front bosses 26can clear the lower edge 42 of the wall opening. Then the box is lowereduntil bottom wall 14 is resting on lower edge 42 of the wall opening. Itcan be seen that the box cannot be removed from the wall opening whileit is in the position shown in FIG. 7, since there remains aninterference or overlap between upper front and rear bosses 22' and 24and the upper edge 40 of the wall opening. As long as bottom wall 14 ofthe box is resting on lower edge 42 of the wall opening, the box cannotbe removed from the opening.

The purpose of resilient spring arms 32 will now be appreciated. Asshown in FIG. 7, spring arms 32 are deflected downwardly slightly bytheir engagement with upper edge 40 of the wall opening. This downwarddeflection of resilient spring arms 32 create a downward force on theentire box, thus assuring that it remains seated on lower edge 42 of thewall opening. In spite of any jiggling that may occur as a mobile home,for example, travels down an assembly line, the outlet box 10 will notfall out of the wall opening. This is true, in spite of the absence ofany nails or screws holding it in place at this stage of assembly.

It will also be apparent that the above described method of installationis the only way that a box so dimensioned can be installed. Thus, if thefirst step of an attempted installation were to seat bottom wall 14 onlower edge 42 of the wall opening, there would still be an interferencebetween the upper edge of upper front boss 22 and the upper edge 40 ofthe wall opening, preventing complete insertion of the box. Since upperbosses 22 are longer or higher than lower bosses 26, the

box can only be installed by the sequence shown in FIGS. 5 through 7.

The installation of an electrical unit 46 such as a plug receptacle orswitch, will now be described. The electrical unit 46 is shown inphantom in FIG. 8, since its particular nature and dimension is notsignificant. Such units are typically provided with a pair of metalmounting or securing straps 48, one extending upwardly and the otherextending downwardly from the front face of such a unit. Theseconventional mounting straps 48 are secured to outlet box by theprovision of upper and lower tapped holes 50 and 52 in upper rear boss24 and lower rear boss 28, respectively. Screws 54 pass throughclearance holes in mounting straps 48 and thread into these holes 50 and52.

The tightening of screws 54 serves a second function. The outerextremities of mounting straps 48 are conventionally broadened into asomewhat T-shape, so that they will bear upon upper and lower frontbosses 22 and 26, respectively. Thus, tightening of screws 54 functionsto clamp or squeeze together the respective front and rear bossesagainst wall panel 36. This permanently anchors outlet box 10 within thewall panel.

Screws 54 serve still a third function, best shown in FIG. 8. The shankof the screws function to eliminate a substantial portion of thevertical play which exists between the top and bottom walls of the boxand the upper and lower edges of the wall opening, thus further assuringthat the outlet box will not be unintentionally removed from the wall.

As shown in F IG. 8, mounting straps 48 are provided with a pair ofthreaded holes 56, which may serve as the anchoring point for the faceplate which conventionally covers the completed installation.

Referring in particular to FIGS. 1 and 3 of the drawings, the provisionfor a supplementary lateral anchoring nail will now be explained. Somelocal building codes require that the outlet box be nailed to anadjacent stud. For this purpose, top wall 12 has a series of three nailguiding grooves. A first of these 58, is a semi-cylindrical groove inthe rear portion of rear boss 24. Two additional semi-cylindricalgrooves 60 are formed in side bosses 30. Together these are sufiicientto anchor a nail along axis 62 of FIG.' 1, since in combination thethree grooves restrain a nail against any lateral movement while stillbeing simple to mold.

Similarly, bottom wall 14 of box 10 is provided with a centralsemi-cylindrical nail groove 64 on the rear of rear boss 28, and with afurther pair of oppositely directed semi-cylindrical side grooves 66 onbosses 34. These three grooves cooperate to provide an anchoring meansfor a lower lateral nail along axis 68 shown in FIG. 1.

It is to be emphasized that the provision for anchoring nails describedabove is only for compliance with certain local building codes, and isnot essential to the secure anchoring of box 10 within a wall opening.

The particular dimensions referred to above are included merely to showexemplary relationships or relative sizes between the outlet box and thewall opening, it being understood that only the degree of play andinterference between the various elements is significant. Similarly,while the mounting bosses have been described as located on the top andbottom walls of the outlet box, they could be mounted on any opposedpair of walls, the principle of operation being the same. As illustratedand described, however, gravity aids spring arms 32 in maintaining theposition of FIG. 7. The number of mounting bosses is also subject tovariation, it being essential only that there be some restraining memberto engage both front and rear faces of the wall panel at opposed sidesof the outlet box.

This invention may be further developed within the scope of thefollowing claims. Accordingly, the above specification is to beinterpreted as illustrative of only a single operative embodiment ofthis invention, rather than in a strictly limited sense.

l now claim:

1. An open front molded plastic electrical outlet box adapted to bemounted in a wall panel opening, comprising:

at least one pair of parallel opposed side walls;

each side wall of said pair having at least two outwardly projectingmounting bosses spaced rearwardly of each other, enough to snuglyreceive the wall panel therebetween, the distance between the outer endof the corresponding mounting bosses of said opposed side walls beinggreater than the corresponding dimension of the wall panel opening,whereby the bosses of each of said side walls are adapted to overlap theadjacent wall panel edges when the box is installed therein to normallyprevent unintentional removal of the box therefrom;

the box and mounting bosses being so dimensioned relative to eachotherthat a first dimension measured from the outside of the first of saidside walls to the outer end of a mounting boss on the other of said sidewalls is greater than a second corresponding dimension measured from theoutside of said other side wall to the outer end of a mounting boss onsaid first side wall, while the corresponding dimension of the wallpanel opening in which the box is adapted to be installed liesintermediate said first and second dimension;

whereby insertion or removal of the box from the wall panel opening ispossible only when the portion of said other side wall between themounting bosses thereon is brought substantially into contact with theadjacent edge of the wall panel opening to permit the mounting boss ofsaid first side wall to clear the adjacent edge of the wall openmg.

2. The outlet box of claim 1, wherein the rearward mounting boss of eachside wall of said pair has a forwardly exposed threaded hole forreceiving the shank of the screw to be threaded rearwardly therein afterthe outlet box is mounted in the wall opening, said threaded holes beingso placed to align with the mounting strap screw holes of conventionalelectrical units to be mounted within the outlet box;

whereby a single pair of screws functions to simultaneously secure anelectrical unit within the outlet box and to firmly secure the outletbox in the wall panel, the head of the screws bearing upon and pressingthe mounting straps rearwardly against the forward mounting bosses assuch screws are threaded into the rearward mounting bosses to therebyclamp the wall panel between the mounting bosses, the shank of suchscrews lying between the adjacent side walls of the box and wall panelopening edges to reduce the play therebetween.

3. The outlet box of claim 1 wherein said other side wall has mountedthereon outwardly biased resilient means positioned to engage theadjacent edge of the wall panel opening to normally bias the outlet boxtoward the wall opening edge adjacent said first side wall, thereby toaid in preventing unintentional removal of the outlet box of the wallpanel.

4. The outlet box of claim 1 which is intended to be mounted in avertical wall panel opening, and wherein said first side wall of theoutlet box is its bottom wall and said other side wall of the outlet boxis its top wall.

5. The outlet box of claim 4 wherein the rearward mounting bosses eachhave transverse nail-receiving passages and wherein said bottom and topwalls of the box each have additional bosses carrying nail-receivingpassages so positioned that the nail-receiving passages of both thebottom and top walls are laterally aligned to receive a nail drivenlaterally through such bosses to secure the outlet box to a studalongside the outlet box.

6. The outlet box of claim 1, wherein the mounting bosses of each sidewall comprise two laterally spaced forward mounting bosses and arearward mounting boss located between but behind said two forwardmounting bosses.

7. An open front molded plastic electrical outlet box adapted to bemounted in a vertical wall panel opening, comprising:

a top wall and a bottom wall,

each of said walls having two forwardly located laterally spaced andoutwardly projecting mounting bosses and a rearward outwardly projectingmounting boss located between said forward mounting bosses but spacedrearwardly therefrom enough to snugly receive the wall paneltherebetween, the vertical distance between the outsides of said top andbottom walls being less than the vertical length of the wall panelopening, the vertical distance between the outer ends of said top andbottom mounting bosses being greater than the vertical length of thewall panel opening, whereby said bosses are adapted to overlap theadjacent wall panel edges when the outlet box is installed therein tonormally prevent unintentional removal of the outlet box therefrom;

the outwardly projecting length of said top mounting bosses beinggreater than that of said bottom mounting bosses and the verticaldistance between the outside of said top wall and the outer or bottomends of said bottom mounting bosses being slightly less than thevertical length of the wall panel opening to permit insertion forremoval of the outlet box from the wall panel opening only when theportion of said top wall between the mounting bosses thereon is broughtsubstantially into contact with the upper edge of the wall panel openingto permit the bottom mounting bosses to clear the lower edge of the wallpanel openings;

each of said rearward mounting bosses having a forwardly exposedthreaded hole so positioned to receive the shank of the screw to bethreaded rearwardly through the mounting straps of a conventionalelectrical unit to be placed within the outlet box after the outlet boxis installed in the wall panel opening;

whereby a single pair of screws function to simultaneously secure anelectrical unit within the outlet box and to firmly secure the outletbox in the wall panel, the head of the screws bearing upon and pressingthe mounting straps rearwardly against the forward mounting bosses tothereby clamp the wall panel between the mounting bosses, the shanks ofsuch screws lying between the top and bottom walls of the box and therespective adjacent edges of the wall panel opening to reduce thevertical play therebetween.

8. The outlet box of claim 7 wherein said top wall has mounted thereonoutwardly biased resilient means positioned to engage the upper edge ofthe wall opening to normally bias the outlet box downward against thelower edge of the wall opening, thereby to aid in preventingunintentional removal of the outlet box from the wall panel.

1. An open front molded plastic electrical outlet box adapted to bemounted in a wall panel opening, comprising: at least one pair ofparallel opposed side walls; each side wall of said pair having at leasttwo outwardly projecting mounting bosses spaced rearwardly of eachother, enough to snugly receive the wall panel therebetween, thedistance between the outer end of the corresponding mounting bosses ofsaid opposed side walls being greater than the corresponding dimensionof the wall panel opening, whereby the bosses of each of said side wallsare adapted to overlap the adjacent wall panel edges when the box isinstalled therein to normally prevent unintentional removal of the boxtherefrom; the box and mounting bosses being so dimensioned relative toeach other that a first dimension measured from the outside of the firstof said side walls to the outer end of a mounting boss on the other ofsaid side walls is greater than a second corresponding dimensionmeasured from the outside of said other side wall to the outer end of amounting boss on said first side wall, while the corresponding dimensionof the wall panel opening in which the box is adapted to be installedlies intermediate said first and second dimension; whereby insertion orremoval of the box from the wall panel opening is possible only when theportion of said other side wall between the mounting bosses thereon isbrought substantially into contact with the adjacent edge of the wallpanel opening to permit the mounting boss of said first side wall toclear the adjacent edge of the wall opening.
 2. The outlet box of claim1, wherein the rearward mounting boss of each side wall of said pair hasa forwardly exposed threaded hole for receiving the shank of the screwto be threaded rearwardly therein after the outlet box is mounted in thewall opening, said threaded holes being so placed to align with themounting strap screw holes of conventional electrical units to bemounted within the outlet box; whereby a single pair of screws functionsto simultaneously secure an electrical unit within the outlet box and tofirmly secure the outlet box in the wall panel, the head of the screwsbearing upon and pressing the mounting straps rearwardly against theforward mounting bosses as such screws are threaded into the rearwardmounting bosses to thereby clamp the wall panel between the mountingbosses, the shank of such screws lying between the adjacent side wallsof the box and wall panel opening edges to reduce the play therebetween.3. The outlet box of claim 1 whereIn said other side wall has mountedthereon outwardly biased resilient means positioned to engage theadjacent edge of the wall panel opening to normally bias the outlet boxtoward the wall opening edge adjacent said first side wall, thereby toaid in preventing unintentional removal of the outlet box of the wallpanel.
 4. The outlet box of claim 1 which is intended to be mounted in avertical wall panel opening, and wherein said first side wall of theoutlet box is its bottom wall and said other side wall of the outlet boxis its top wall.
 5. The outlet box of claim 4 wherein the rearwardmounting bosses each have transverse nail-receiving passages and whereinsaid bottom and top walls of the box each have additional bossescarrying nail-receiving passages so positioned that the nail-receivingpassages of both the bottom and top walls are laterally aligned toreceive a nail driven laterally through such bosses to secure the outletbox to a stud alongside the outlet box.
 6. The outlet box of claim 1,wherein the mounting bosses of each side wall comprise two laterallyspaced forward mounting bosses and a rearward mounting boss locatedbetween but behind said two forward mounting bosses.
 7. An open frontmolded plastic electrical outlet box adapted to be mounted in a verticalwall panel opening, comprising: a top wall and a bottom wall; each ofsaid walls having two forwardly located laterally spaced and outwardlyprojecting mounting bosses and a rearward outwardly projecting mountingboss located between said forward mounting bosses but spaced rearwardlytherefrom enough to snugly receive the wall panel therebetween, thevertical distance between the outsides of said top and bottom wallsbeing less than the vertical length of the wall panel opening, thevertical distance between the outer ends of said top and bottom mountingbosses being greater than the vertical length of the wall panel opening,whereby said bosses are adapted to overlap the adjacent wall panel edgeswhen the outlet box is installed therein to normally preventunintentional removal of the outlet box therefrom; the outwardlyprojecting length of said top mounting bosses being greater than that ofsaid bottom mounting bosses and the vertical distance between theoutside of said top wall and the outer or bottom ends of said bottommounting bosses being slightly less than the vertical length of the wallpanel opening to permit insertion for removal of the outlet box from thewall panel opening only when the portion of said top wall between themounting bosses thereon is brought substantially into contact with theupper edge of the wall panel opening to permit the bottom mountingbosses to clear the lower edge of the wall panel openings; each of saidrearward mounting bosses having a forwardly exposed threaded hole sopositioned to receive the shank of the screw to be threaded rearwardlythrough the mounting straps of a conventional electrical unit to beplaced within the outlet box after the outlet box is installed in thewall panel opening; whereby a single pair of screws function tosimultaneously secure an electrical unit within the outlet box and tofirmly secure the outlet box in the wall panel, the head of the screwsbearing upon and pressing the mounting straps rearwardly against theforward mounting bosses to thereby clamp the wall panel between themounting bosses, the shanks of such screws lying between the top andbottom walls of the box and the respective adjacent edges of the wallpanel opening to reduce the vertical play therebetween.
 8. The outletbox of claim 7 wherein said top wall has mounted thereon outwardlybiased resilient means positioned to engage the upper edge of the wallopening to normally bias the outlet box downward against the lower edgeof the wall opening, thereby to aid in preventing unintentional removalof the outlet box from the wall panel.